In general, as a countermeasure against high-frequency noise generated from semiconductor devices such as semiconductor packages, a method for implementing a bypass capacitor between a power-supply line and a ground (GND) pattern has been known. However, a capacity of the bypass capacitor is limited, and therefore, it is difficult to sufficiently supply current to a semiconductor device only using current supplied from the bypass capacitor. Therefore, a core power supply unit directly supplies current to the semiconductor device more than a little.
Japanese Patent Laid-Open No. 2004-140210 discloses a countermeasure against high-frequency noise spreading to a printed circuit board which is generated by supplying current from a core power supply unit. Specifically, Japanese Patent Laid-Open No. 2004-140210 discloses a printed circuit board configured such that a stub wiring is disposed between a bypass capacitor and a core power supply unit so that impedance lower than that of a power-supply path is obtained. That is, current including high-frequency noise is allowed to be supplied to the stub wiring and is reflected at an open end whereby noise current supplied from a semiconductor integrated circuit is cancelled.